Lubricant composition



Patented Dec. 18, 1951 UNITED STATES PATENT OFFICE 2,579,038 LUBRICANT COMPOSITION Elliott Alfred Evans and John Scotchford Elliott,

London, England, assignors to C. C. Wakefield & Company Limited, London, England, a Brit'- ish company 6 Claims.

The present invention comprises improvements in or relating to lubricating compositions and relates more particularly, though not exclusively; to lubricating compositions for use in internal combustion engines which may be either petrolor oil-operated. In the latter case the invention is applied to the so-caIled ""heavyduty lubricating oils employed in diesel and other types of oil engines.

It is one object of the invention toprovide a lubricating composition in which the tendencies of the lubricant to form products corrosive to metals (e. g. metal bearing surfaces) and to form deleterious oxidation products in the lubricant are inhibited, and another object is to provide a composition which pbssesse's also detergent properties. The latter properties tend to secure a clean running engine during use of the lubricant by preventing the deposition gum or lacquer on the lubricated parts and by maintainin-g solid particles and sludge (formed in any part of the engine or in the lubricant) in suspension therein. Such properties are of particular importance in oil engines such as diesel engines.

The present invention contemplates theuse in a lubricating composition of a metallic derivative of an organic substituted dithiophosphate, some examples of which latter type of compound have already been proposed for incorporation in lubricating oils.

According to this invention 'a lubricating coniposition comprises a lubricating oil base and a minor proportion of (a) the tin-salt of an oil-- soluble petroleum sulphonic acid and (b) a polyvalent metal salt (which is soluble in the oil base) of an organic dithiophosphoric acid.

It has already been proposed to add a variety of metal salts of organic dithiophosphoric acids to oils.

These additives are known in general. to part to the oil good resistance to oxidation and to inhibit to a greater or less extent the formation of products corrosive to composite metal bearings. v

Some of them also possess detergent or sludge dispersive properties, especially effective in this connection being the alkaline earth metal salts of the straight chain dithiophosphoric acids having ten or more carbon atoms.

It has been found, however, that these dithioof relatively high molecular Weight are much less effective as inhibitors of oxidation and bearing corrosion than those of low molecular weight which latter, however, are relatively inefiective as detergents and sludge dispersing agents. I

An advantage of the present invention lies in the fact that by the use of the combination of additives herein disclesed lubricating compositions can be provided possessing all these proper= ties to a high degree. 7

A further advantage of the compositions of the present invention is that they provide superior protection to ferrous metal surfaces against rust= ing (and consequent wear) due to the presence of condensed Water, carbon dioxide, hydrcbromic acid etc. normally present in small amounts in the combustion space. 4 The additives of the present invention also confer upon the base oil an improved film rupture strength. I V r The combination of desirable features provided by the lubricating compositions of this invention cannot be obtained by the randomsele'ction of any compound possessing detergent properties with any oxidation or corrosion inhibitor, as very often the presence of the detergent inilitates against the normal action of the inhibitor, rendering it relatively ineffective, probably by preventing it from forming a film on the surfaces of metal catalysts that may be prevent. Furthermore many of the detergent compounds formerly proposed as lubricant additives are themselves corrosive to composite metal e. g. copperlead bearings. f

A feature of the present invention is that not only do the two additives not interfere with one anothers normal actions, but also in. many instances they co-operate to give improved results over and above those obtained with either additive used alone. p Y I According to one form of the present invention a lubricating composition comprises a lubri eating oil base and a minor proportion each of the tin salt of an oil soluble petroleum sulphonic acid and a metal salt (which is soluble the oil base) of an organic di-substituted dithiophosphoric acid derived at least in part from an alkylated phenol Such a (ii-substituted salt can be represented by the general formula R101 /YS at s n where n represents the valency of a metal M, R1 is any suitable organic radicle and R2 is an alkyl ated aromatic radicle;

The radicle R2 in the general formula quoted above is conveniently such as to have not less than five carbon atoms in the alkyl group and may be derived, for example, from p-tertia'ry amyl phenol, .p-octyl phenol or octyl cresol. The radicle R1 is such as to provide an oil soluble product and may be derived; for example, from an aliphatic alcohol (e. g. 'butyl amyl or lauryl alcohol), a cyclic alcohol (e. g. cyclohexanol or methyl cyclohexanol), a phenol (e. g. cresol or octyl cresol) or an aromatic alcohol such as benzyl alcohol.

It will be understood that appropriate radicles for R1 and R2 in the general formula quoted above will always be such that the di-substituted metal salt is soluble in the lubricating oil base.

While, as already indicated, it is preferred to employ compounds wherein, R2 contains at least five carbon atoms in the alkyl group, it is within the scopeof the invention to employ compounds in which the alkyl group of R2 is short, or even absent, provided that R is of such a nature as to confer upon the metal salt adequate oil solubility.

Preferred specific examples of di-substituted dithiophosphoric acids .a metal salt of which is employed in accordance with the invention are:

Di(octyl-cresyl) dithiophosphoric acid Octyl-cresyl cresyl dithiophosphoric acid Octyl cresyl 2-ethyl hexyl dithiophosphoric acid Di(p-octyl phenyl) dithiophosphoric acid Di(t-butyl cresyl) dithiophosphoric acid Octyl cresyl n-butyl dithiophosphoric acid Octyl cresyl cyclohexyl dithiophosphoric acid Preparation of such metal salts is conveniently effected by first reacting the alkylated phenol with phosphorus pentasulphide with or without the presence of an appropriate hydroxylic organic compound for simultaneous reaction to produce a mixed di-substituted dithiophosphate. The acid is conveniently neutralized with caustic soda and a desired metal salt produced by the addition of a suitable salt of the said metal.

According to another form of the present invention the lubricating composition last referred to is modified by the incorporation in the lubricating oil base (either in place of or in addition to the organic di-substituted dithiophosphate derived from an alkylated phenol) of a minor proportion of an'oil soluble metal salt of an organic di-alkyl or di-cycloalkyl dithiophosphoric acid. The last-mentioned salt is represented by the following general formula:

where R1 and R2 are alkyl or cyclo-alkyl groups having at least five and preferably not more than ten carbon atoms either in a straight or branched chain or ring. and where nrepresents the valency of the metal M.

Radicles R1 and R2 of the formula quoted above are preferably, but not necessarily, similar and may, for example, be derived from amyl alcohol, the hexyl alcohols such as n-hexyl alcohol, methyl isobutyl carbinol and 2-ethyl butanol, 2 ethyl hexanol, nonyl alcohol, cyclohexanol and methyl 'cyclohexanol.

Preferred specific examples of di-alkyl or dicycloalkyl dithiophosphoric acids, a metal salt of which is employed in accordance with the present invention, are:

dithiophosphoric acids may be employed the production of the oil soluble salts.

Preparation of the di-alkyl or di-cycloalkyl dithiophosphates may be effected by first reacting an appropriate alcohol or mixture of alcohols with phosphorous pentasulphide to produce the thiophosphoric acid from which the desired metal salt may be prepared for example by first neutralising the acid with caustic soda and then adding a suitable salt of the metal the dithiophosphate of which is desired. It is possible,

\ however, to prepare certain salts, e. g. those of zinc by direct reaction of a metal oxide with the dithiophosphoric acid.

According to one form of the invention a chromium salt of the organic (ii-substituted dithiophosphate is employed, the desirability of employing organic compounds of both tin and chromium in a lubricating composition having been already proved. "f Other dithiophosphate salts may, however, be employed such as those of barium, calcium, strontium, magnesium, zinc, aluminium, nickel, cobalt, tin, cadmium and manganese.

According to the invention also the lubricating compositions of the kind above referred to may also include in its composition (1) a hydroxysubstituted aromatic thioether and/or dior polysulphide, and/or (2) an aromatic phosphite or thiophosphite ester derived from such an aromatic thioether and/ or dior polysulphide. As an alternative to ingredients (1) and (2) or in addition thereto a yet further ingredient viz. (3) a tri-aryl phosphite may be included in the lubricating composition.

As examples of the third addition agent may be quoted:

(l) Di(3-carbomethoxy-4-hydroxyphenyl) thioether, disulphide or polysulphides.

(2) Di(3-carbomethoxy-4-hydroxyphenyl) thioether cresyl phosphite.

(3) Triphenyl phosphite, tri(p.t-amyl phenyl) phosphite.

EXAMPLE 1 Preparation of chromium d2'(octyZ-cresyl) dithz'o phosphate 88 grams of octyl cresol (a mixture of diisobutyl cresols commercially available) were placed in a 250 c. c. round-bottomed flask, heated to the phosphorus pentasulphide had disappeared.

The reaction was then completed by heating slowly to 150 C. and maintaining this temperature with stirring for five minutes.

After cooling, the product was dissolved in petroleum ether and filtered from a little sulphur and unreacted phosphorus pentasulphide, the solvent being then distilled off under reduced pressure, yielding an amber viscous liquid.

The acidity of the product, determined by titrating an alcoholic solution with standard caustic soda solution in the presence of a phenolphthalein indicator, corresponded to an apparent molecular weight of 529 as compared with weight of water in a beaker, heated to id-50 C.

a theoretical molecular weight of 533 for di(octylcresyl) dithiophosphoric acid. This product was mixed with nine times its and neutralised by adding caustic soda solution gradually with stirring until alkaline to phenolp t a ein indicator.

aeraosa After cooling, the aqueous solutionwa's decanti ed from this liquid which was then dissolved in petroleum ether, dried :over anhydrous sodium sulphate, filtered, and freed from solvent by distillation. An 82% theoretical yield of the prodnot was obtained.

Of a number or products prepared by this method, one typical one prepared on a larger scale had the following approximate analysis:

Chromium, 1.20%} sulphur. 8 45%; phosphorus,

4.3% Chromium salt of di-(octyl-cresyD-dithiophosphoric acid, 43% Sodium salt of di('octyl-cresyl)dithiophosphoric acid,

Free di(oc-tyl-cresyl)dithiophosphoric acid, 29%

Octyl cresoi and other neutral products, 23%

(The molecular weight of the free acid in this case was 600.)

The mixed product obtained by this method is referred to subsequently as chromium di- (octyl-cresyl) dithiophosphate A.

EXAMPLE 2 of molecular weight about 675 had the following analysis:

Chromium, 1.86%.; phosphorus, 4.34% Chromium salt of di(octyl-cresyl)dithiophosphoric acid, 72%

Sodium salt of diioctyl-cresyl)dlthiophosphoric acid, 13%

Free di(octyl-cresyl)dithiophosphoric acid, 15%

This product is referred to subsequently as chromium di(ootyl-cresyl)dithiophosphate B.

It will be understood that in employing the compounds of this invention either pure metal salts may be used, or mixtures such as products of Examples 1 and 2. While minor amounts of the free dithiophosphoric acids and their sodium salts in the products are not objectionable it is preferred to utilise materials containing not more than about 20% of the free acid (and preferably less) and not less than about ofthe polyvalent metal salt.

If desired, the residual free acid may be substantially neutralised by heating the product (preferably in oil solution) with a metal oxide or hydroxide (such as zinc oxide or calcium or barium hydroxide) to produce, for example, a mixture of chromium and zinc salts associated with a minor amount of sodium salt.

EXAMPLE 3 Using the method of Example 1, 1170 grams of Z-ethyl hexanol were reacted with 500 grams of phosphorus pentasulphide, a reaction tem- Chromium salt of di(2-'ethyl hexyl) peratureoi 1'00 to C proving adequate and the reaction being concluded by heating to 130 C. A dark liquid was obtained having a molecular weight of '380 as compared with a theoretical molecular weight of 354 fordi(-2-ethyl hexyl) dithiophosphoric acid.

The zinc salt of the flatter :acid was prepared in the present example by heating a mixture of 101 grams of the acid and 11.1 grams oi zinc oxide for half an "hour at C. to C. The reaction product was dissolved petroleum ether, filtered from excess of zinc oxide and the solvent removed by distillation to yield a yellow viscous liquid having 8.30% by weight of "zinc as compared with a theoretical amount or 8.22% for zinc dioctyl 'dithi'ophosphate'.

EXAMPLE 4.

Tin salt 0'7 octyl cresyl Lethyl h'ezcyl dithiophcspho'rzc acid Using the method of Example 1, there were obtained from a mixture of 330 grams of octyl cresol and .195 grams of 'Z-ethyil 'hexanol by the action of 166.5 grams of phosphorus .pentasiilphide, 64'? grams of a viscous amber liquid, representing a 97% yield,

This had a molecular weight of 540, as compared with a theoretical value of 444.

Using the method of Example 2, there were obtained from 42 grams of this material, and 12.4 grams of stannous chloride in cold concentrated aqueous so'hition, 34.6 grams (72%) of an extremely viscous brown liquid containing 12.5% of tin.

EXAMPLE 5 M fired chromium-zinc salt of di(2-ethyl .hemy'lt) .ctit'hiophosphoric acid 19 grams or di 2-ethyl hexyl) dithiophosphoric acid '(-of M. W. 380) prepared as described in Example 3 were stirred for 20 minutes at YO-80 C. with moist chrom'ic hydroxide freshly precipitated trom a 10% aqueous solution containing 4.2 grams of chrome alum by the addition of ammonia. 1. 5 grams of zinc oxide were then added and the heating continued for a further 15 minutes, after which the temperature was slowly raised to 130 C. to complete the reaction and eliminate the water formed.

The product, after dissolving in petroleum ether, .filtering and removal of solvent, contained 1.30% of chromium, and 5.10% of zinc, the composition being approxima-tely as follows:

dithiophosphoric acid, 29%

Zinc salt of di(2-e'-thyl hexyl) dithiophosphori'c acid, 67%

Free diiZ ethyI hexyl) dithiophophoric acid, 3%

Other known methods for the preparation of the metal dithiophosphates of this invention may also be employed e. g. direct reaction between the free acid and a metal oxide in alcohol-benzene solution at 40-50 C. (applicable especially to the alkaline earth metal and magnesium salts), or direct reaction between a metal hydroxide, such as barium hydroxide and the free acid by heating together in mineral oil solution in presence of a current of air to remove liberated water.

Alternatively metathesis may be carried out in alcoholic solution between an alkali metal salt of a dithiophosphoric acid and an alcohol soluble metal salt.

Many of the salts can be prepared in. goodyield by the method of Example 2, the conversion to :7 the metal salt being in many cases .(e.,g. .tin, cadmium, nickel,,cobalt) vmore satisfactorythan that obtained. in'the case of chromium. Better conversion is also obained in the case of the dialkyl dithiophosphates than with the alkylated aryl dithiophosphates.

EXAMPLE 6 Tin petroleum sulphonate for use in conjunctionwith the product of Examples 1 to was prepared as follows: A

4 lbs. of an oil-concentrate containing 45% of sodium petroleum sulphonate (derived from the so-called mahogany acids of molecular weight about 400 to 420) was mixed with 3 gallons of water and heated to 90 C.. a milky solution being obtained. To this solution was added while being stirred, a cold solution of lb. of stannous chloride tSnClzZHzOi-in 500 cos. of water. Tin petroleum sulphonate in oil solution was precipitated.

After cooling, the aqueous solution was decanted and the product washed by boiling with 1 gallon of water. The boiled mixture was further mixed with 4 lbs. of mineral oil and the resulting composition passed through a De Laval centrifuge. The oil concentrate mainly free from water was heated at 250 F. in a stream of air to remove further moisture.

By this procedure there was obtained '7 lbs.

which serve to illustrate in various respects the desirability oflthe lubricating compositions pro.- vided by the present invention.

For purposes of comparison, test results include those for unmodified lubricating oil bases employed in producing the examples of composi tions proposed by the present invention, and also, in certain instances, for compositions including only one of the additives. The constituents of said compositions are given in percentage proportions by weight in all tests.

Test 1.-O:r2'dation resistance As a means of examining the oxidation resistance of the compositions proposed by the present invention, a modification of the well-known British Air Ministry oxidation test was'employedr In this test 40 cos. of the oil were oxidised by heating at 160 C. for two periods of 6 hours in glass tubes in the presence of a stream of airblown through at a rate of 15 litres per hour. Lubricating compositions were oxidised under the standard conditions of the British Air Ministry oxidation test except that a temperature of 160 C. was employed and that a copper catalyst, consisting of a rolled polished piece of cop per foil 2%" x 1", was present. Thecatalyst was replaced by a fresh one at the end of the first period of 6 hours oxidation.

The test results obtained were:

Lubricating Composition Per cent insoluble in petroleum ether (B. P. below 40 C.)-

Acidity (mgs. oi

Viscosity Increase (per cent) gram Oil

+0. 5% Tin Petroleum sulphonate Trace.

Very slight trace.

Slight trace.

19. 3 Trace.

Oil 13" as employed in these and in ensuing tests consisted of a blend of 94% of a solvent refined parafl'lnic type mineral oil of viscosity about 150 seconds Redwood at 140 F. and 6% of a blend of viscosity about 330 seconds Redwood at 140 F. containing a brightstock.

While the terms minor proportion" would cover the use of the additives of this invention in a general way, the following proportions give an indication of. the amounts contemplated:

The metal dithiophophate, 0.1-2% (preferably 0.2-1%) The tin petroleum sulphonate, 0.05-2% (preferably 0.1-1%) 1 a The third additive, 0.01-1% 1 TEST RESULTS Numerous examples of the invention a re given below in conjunction with the results of tests (preferably 0.05- 1 It would seem that whereas all the compositions tested have greatly improved oxidation resistance as compared with the base oil, those comprising metal salts of alkylated aromatic dithiophosphates are especially effective, particularly as regards the inhibition of sludge formation.

Test 2.Bearing' corrosion The following test was employed for obtaining information as to the tendency for corrosion of composite metal bearings, particularly co perlead hearings, to occur in use of lubricating compositions provided by the invention.

400 ml. of lubricant was weighed into 1500 ml. tall lipless glass beakers, eight of which were heated in a circular electrically heated oil bath thermostatically controlled to maintain the lubricant temperature at C. The beakers were equipped with closely fitting aluminum covers having central slides which were normally closed but capable of being opened for the. insertion of a test specimen. The slides when closed allowed suflicient clearance for centrally placed steel stirring rods to revolve freely. The latter were electrically driven. from a common driving shaft at 400:40 R. P. M. and carried at their lower. end slotted holders .to which lead test pieces" were attached by means of screws: For additives of this invention than would be ohthe test-pieces rectangular plates of purelead tamed. by the use of either additive separately 1%" by 1 were mounted vertically just below in comparable proportions; and that further-'- the surface of the lubricant with the: longer. axis more the use of tin petroleum sulphonate gave horizontal. Copper strips, as catalysts; wide results su erior to those obtained by the use of and. bent. into a semicircle 3%" in diameter were other metal petroleum sulphonatessuch as those placed Wholly below the surface of the lubricant of calcium and sodium, especially as regards and attached by means of vertical copper wires the retardation of the rate of-increase of corrosion to corks fitted in the beakercovers. Each" beaker inthe later stages oi the test. The remaining was also fitted with a thermometer. test'results are quoted to illustrate the wide range Tests were conducted for a maximum total of compounds and proportions which may be time of 30 hours in periods or six hours, the copemployed in order to obtain lubricating composiper and lead specimens being removed every two tions possessing a high degree of resistance hours 9/1101?repl'cmedI y fresh c n es- C01 against the formation of products corrosive to per catalysts were cleaned withcarborundum composite metal bearings. powder and washed in petroleum ether. Lead specimenswere flattened, scraped witha spe- Test 3.-Protection against rusting cial Ska-rtsen scraper and finally po1ished,. by brushing in one direction th a t tiff Asimple test'was devised to demonstrate the Wire brush. known-,as m carding b for Wash, effectiveness of the lubricating compositions of ing in benzene and Weighing; t 2.1m thisinvention inafiordingprotection against the period th washing in benzene;- brushing; rusting of. ferrous metal surfaces in presence of with a camel hair brush. and re-weighingrwas efmoiisture carbon dioxidefected. The cumulative corrosion at any given Rectangular plates of mild S l X time was'ca'lculated by adding together theweight i'shed with emeri lo h and wa he w h p losses on the lead: specimens after each 2-hour" ao leum ether, were weighed and completely imperiod. These, cumulative losses were plotted: against time, and from the curves obtained, the times required for certain fixed corrosion losses tobe reached, were read off.

The following. results were obtained:

10 It will be seenv from the foregoing test results, and particularly from tests 843, that a higher degree of protection against corrosion is obtained by the use of the combination of mersed in the? oil under test for five seconds at roomtemperature, allowed to drain in a vertical position for 15 minutes, and placed horizontally across two short pieces of glass rod at the bot- 35" tom of a 4* diameter glass dish.

Lubrioatingcomposltion Lead specimen weight loss (digs) after- Hours rim to welghtlossof 18 hrs. 'mgs.

mgs.

thiophosphate 1 011% Tin petroleum sulphonate: Oil .13 '+:0.5% Nicke1 di(1nethyl"cyclohexyDdithio phosphate 0.2% Tm petroleum 'sulphonatei Oilr fiB? +1 0.6%;Mangancse di(tertiary.- bu yl) dithiophosphate V 014%"Ti11 petroleumsulphonate: Oil B -i.. O'.8%.'I.in octyl cresyl 2etl1y1 hcxyl-dithio phosphate l 25% Tinpetroleum'sulphonate .Oil B" 2.0% Zinc di(2-ethylhexyDdithiophosphate; 0.2% Tin Petroleum Sulphonate +02% tri(p-tertiary amyl phen-yl) phosphite. Oil B 0.5% Zinc di(methyl cyclohexyl) dithiophosphate 2.0% Tin -petrolcum' -sulphonate; 0.5% Octyl crcsol thioether over 30 over 30 I over 30' 1 Figures quoted against tests marked thus were-the meanof 2 or 3 tests! The-compound described as oct yl -cresol' thioether test-No.- 22- was-prepared bythe action of sulphur dichloride on o'ctyl cresol in carbon tetrachloride solution;

It would seem that to: obtain thekm'ost' efiectlv'e inhibition ofcorrosion; the: amount of tin petroleum sulphonate employed should not exceed the amount of 'm'etal dithiopho'sphatez 7 muslin, and weighed.

Th'edish was then filled with distilled water saturated. with carbon dioxid so that the steel 0 was-approximately belowthe surface ofthe water andallowed to stand open to the air, the level being kept approximately constant.

After standing for one. month, the plates were v removed, freed from loose rust by rubbing with The following results were obtained:

Test 5.Lauson engine tests T t Loss in weight Oil used of e (milligrams) Tests were carried out in standard H-2 type 6 Lauson engines, under the following conditions:

23..-" B 13.1 "15E... 41.7 24. Oil B+0.5% Zinc di(e-met y isoamy ir e an t I D Jacket temperature 210-v -2' F. r mm 00 crcs figmo hog hate Bu y 3 1 011 sump temperature 280i2 F. 0.2% Tin Petroleum sulphonate. 0.05% di(3-carbomethoxy-4- Test Duration 60 hours hydroirlyphenybthioether cresyl hos ite. p p Test results were as follows:

Used Oil Analysis Piston lacquer rating Per cent Lubricant ((30. R. Bearing insol. in p visweight Per cent pet. ether Acid ual loss visc. inc. (B. P. y rating) (mgs.) below 40 C 28 Oil B (average of over tests) 6.2 92 39,9 0, 94 04 29 Oil B+0.6% chromium di(octyl cresyl) dlthlo- 7.3 6 20.4 0. 64 0.28

phosphate B." V As test 29+0.2% tin petroleum sulphonate 8. 4 i 10 28, 0 0, 2 0 5 31 Oil B+0.6% chromium di(octyl cresyl) dithlo- 8.5 39 33.3 0.70 0.60

phosphate A+O.2% tin petroleum sulphonate. 32 As test 3l+0.2% di(3-carhomethoxy-4-hydroxy- 7. 9 7 33. 8 0. 61 0. 63

phenyl) thioether cresyl phosphite. 33. As test 3l+0.l% di(3-carbomethoxy-4-hydroxy- 8. 5 17 34, 5 0,94 (139 phenyl)polysulphide. Oil1;B"1-1i0.5% zinc di(a-methyl isoamyl) dlthlo- 7. 5 5 16. 0 0. 41 0.28

osp ate. A: test 34+0.5% tin petroleum sulphonate 9. 0 8 23 6 0,10 0, 2 As test 34+l.0% tin petroleum sulphonate 9. 5 17 19, 0 Z 0 06 0 As test 34+0.2% tin petroleum sulphonate+0.2% 9.0 6 13.8 0.12 0.21

chromium di(octyl cresyl)dlth1ophosphate B. 38.. Oil B+0.6% zinc octyl cresyl 2-ethyl hexyl di- 8, 7 18 16, 4 17 Q 39 thiophosphate+0.2% tin petroleum sulphonate. 39... Oil B"+0.6% chromium octyl cresyl 2-ethyl hexyl 8. 6 6 20. 0 0.14 0. 42

dithiophosphate+0.2%t1n petroleum sulphonate. 40. Oil B+0.6% chromium di(2-ethyl hexyDdithlo- 7. 7 7 25. 6 0:05 0. 34

phosphate+0.2% tin petroleum sulphonate.

The water in test 23 wasfull of red rust where as that in test 24 was only slightly afiected. Test 4.Protection against rusting in presence;

of hydrobromic acid 7 l The method of British Ministry of Supply specification D. T. D. 698 (Appendix 1) was em- -Q5 signed to simulate conditions in an internal combustion engine where, after a period of running the engine is allowed to remain idle. Corrosion of e Cylinder Walls, With consequent 08s of quantity to effect by itself adequate protection.

power due to unduly large piston clearances,

thereupon tends to take place due to the presence of condensed moisture, carbon dioxide, and fuel combustion products, notable among which is hydrobromic acid produced in small quantities from the combustion of the ethylene dibromide normally present in leaded fuel.

The following results were obtained:

Gain in weight of steel strips due to rust formation (milligrams) Test Na Oil used 1 Figures quoted are the mean of at least three tests.

The C. R. C. visual rating was according to the method laid down by the Co-ordinating Research 0ouncil for rating piston cleanliness in the standard Chevrolet 36-hour L-4 test, in which a clean piston would have a rating of 10.0.

/ Thermajority of the figures quoted were the mean of at least two tests.

It will be seen from the results of tests 29 an and 30 and 34 to 37 that the combination of two additives according to the present invention yielded results superior to those obtained by the use of the metal dithiophosphate only, as regards piston cleanliness.

The advantage of a third addition agent as proposed by this invention is demonstrated by the results of tests 31 to 33, in which the metal dithiophosphate was present in insufficient additional improvement as regards oil oxida-' ticn might be expected from the employment with tin petroleum sulphonate of both a metal dialkyl dithiophosphate and a metal alkylated aryl dithiophosphate.

Further tests-were carried out in standard H- 5 type Lauson engines, under diiierent conditions,

as follows:

Jacket temperature F 350 Oil sump temperature F 225 Duration hours duty conditions as in high-speed diesel engines operating under heavy load.

Tests results were as follows:

, i'uIsedxQlI Amman. how-sin Pit B i Y uer ra mg is on ear rig: 'lllfgt Lubmam 1%};110, rings Wt. loss,

visual stuck (mgsJ -Percentrating) zv pr H 95 Oil 13' 1.5 i 1 118 176.1 Oil B"-(repeat test) 1.5 l 2 109; r 197, 01 Oil B+0.7% diQ-methylisoalpyl) zinc 3.2, 1 12 137.1 dithiophosphatel l I on "Bi s-0.5% dua-meth i o l). zinc 7.5 None 14 1 m.

' dithiopho'spliate "+06% tin petroleum sulphonate.

The considerable superiority of the combination of additives or the present invention was thus amply demonstrated.

Test 6-.36 hour Chevrolet test 2 Tests were carried out on a 6-cylinder Chevrolet engine of standard type and according to the standard Co-ordinating Research Council procedure L-4.

leum sulphonate and an oil' soluble metal salt of an organic diZ-SubstitutBG' dithiophosphorlc; acid. We claim:

A.,lubricating composition; which comprises,

0 a hydrocarbon lubricating oil base in major proportion between 0.05% and 2.0% by weight of said base, a proportion between 0.05% and 2.0% by weight of said base of a tin salt of an oilsoluble petroleum sulphonic acid and a propor- Average Test Corrosion Piston Total Total No Oil Composition loss per Varnish Varnish Sludge whole Rating Rating Rating brg.

45 0.856 8.4 48.4 4 .0 46... Oil B+0.6% Chromium di(octy1 cres yl ditlnophosphate) 0.2511 0 Igg- Petroleum Sul- 0 109 9- 2 a 4 41 0.2% di(3-carbomethoxy-4- hydroxyphenybthioether cresyl phosphite. 47- Oil B+0.5% 7igngigliiw-fimethglt isoamy op osp a e. +0 5% tin petroleum 0.192 8.95 48.95 46.4

phonete. 48"... Oil B"+0.5% Zinc di(a-methyl isoamyl) dithiophosphate. 0.2% tin petroleum sulphonate. cfisyfi 11mm 0.127 8.85 48.85 43.9 dithiophosphate "B 0.05% di(3-carbo1 nethoxy-4- hydroxyphenyl) thioether cresyl phosphite.

Used Oil Analysis (36 hours) Per cent N iinsolitble A id t Test 0. 11 pe roc i y e er per increase (3 gram) below 40 C In all the foregoing examples, the tin petroleum sulphonate employed was prepared as described in Example 6.

It will be understood that in all the foregoing tests the metal dithiophosphate additives were employed as prepared by the methods already illustrated, some being relatively pure organic compounds and others associated with varying minor amounts of other compounds, notably the free dithiophosphoric acids and their sodium salts.

The invention will be understood as including an additive for use in a lubricating oil base, which additive comprisesin admixture tin petrotion between 0.1% and 2.0% by weight of said base of an oil-soluble chromium salt of an octyl cresyl dithiophosphoric acid.

2. A lubricating composition in accordance with claim 1 in which the chromium salt is from 0.3 per cent to 2 per cent, the tin salt is from 0.05 per cent to 0.5 per cent by weight of the base and the proportion of the tin salt is never more than that of the chromium salt.

3. A lubricating composition in accordance with claim 1 in which there is included, in an amount from 0.1 per cent to l per cent by weight of the base, a derivative of a hydroxy substituted aromatic thioether selected from the group consisting of di(3-carbometh0xy-4-hydroxy phenyl) thioether cresyl phosphite and (3-carbomethoxy- 4-hydroxy phenyl) polysulphide.

4. A lubricating composition which comprises a hydrocarbon lubricating oil base in major proportion, a proportion between 0.05 per cent and 2 per cent by weight of said base of a tin salt of an oil-soluble petroleum sulphonic acid, and a proportion between 0.1 per cent and 2 per cent by weight of said base of an oil-soluble chromium salt of an organic dithiophosphorlc acid. selected from the group consisting of chromium di(octyl cresyl) dithiophosphate, chromium di(p-octyl phenyl) dithiophosphate, chromium dim-methyl isoamyl) dithiophosphate, chromium di(2-ethy1 -15 hexyl) dithiophosphate, chromium octyl cresyl 2-ethyl hexyl dithiophosphate, and chromium octyl cresyl cresyl dithiophosphate.

5. A lubricating composition in accordance with claim 4 in which the chromium salt is from 0.3 per cent to 2 per cent, the tin salt is from 0.05 per cent to 0.5 per cent by weight of the base and the proportion of the tin salt is never more than that of the chromium salt.

6. A lubricating composition in accordance with claim 4 in which there is included, in an amount from 0.1 per cent to 1 per cent by welght of the base, a derivative of a hydroxy substituted aromatic thioether selected from the group consisting of .di (8-carbomethoxy-4-hydroxy phenyl) thloether cresyl phosphiteand (3 -carbomethoxy-4-hydroxy phenyl) polysulphide. V ELLIO'IT ALFRED EVANS.

JOHN SCOTCHFORD ELLIOTT.

REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 2,125,936 Liberthson Aug. 6, 1938 2,228,659 Farrlngton et al. Jan.'14, 1941 2,252,984 Rutherford Aug. 19, 1941 2,322,307 Neely et a1. June 22, 1943 2,344,392 Cook et a1. Mar. 19, 1944 2,369,632 Cook et a1. Feb. 13, 1945 2,383,917 Morgan Aug. 28, 1945 2,414,257 Evans et a1 Jan. 14, 1947 2,417,876 Lew-is Mar. 27, 1947 2,418,422 Palmer Apr. 1, 1947 

1. A LUBRICATING COMPOSITION, WHICH COMPRISES, A HYDROCARBON LUBRICATING OIL BASE IN MAJOR PROPORTION BETWEEN 0.05% AND 2.0% BY WEIGHT OF SAID BASE, A PROPORTION BETWEEN 0.05% AND 2.0% BY WEIGHT OF SAID BASE OF A TIN SALT OF AN OILSOLUBLE PETROLEUM SULPHONIC ACID AND A PROPORTION BETWEEN 0.1% AND 2.0% BY WEIGTH OF SAID BASE OF AN OIL-SOLUBLE CHROMIUM SALT OF AN OCTYL CRESYL DITHIOPHOSPHORIC ACID. 